The present invention relates to an air supply and exhaust apparatus that forms air curtain flow surrounding outer circumference of a specified local region and that exhausts air in the local region inside the air curtain flow by sucking the air in a direction opposite to the air curtain flow.
As ventilating apparatus for ventilating a specified local region, for example, the inventor and others have already proposed apparatus that supply airflow like air curtain surrounding the local region while suck and exhaust air in the local region inside the air curtain flow.
FIG. 13 shows an example of the apparatus.
In FIG. 13, reference numeral 4 denotes a fresh-air supply chamber that is, for example, generally conical in shape and that is provided over the local region. Immediately beneath the fresh-air supply chamber 4, a suction hood 10 shaped like a dome having a comparatively shallow depth and spreading along a direction of exhaust is detachably provided a specified distance apart from the chamber so as to have an opening edge 10d projecting downward from a bottom opening surface of the fresh-air supply chamber 4 by a specified size. Between the fresh-air supply chamber 4 and the suction hood 10 inside the chamber, as a result, a supply air swirling space having passage diameters increasing gradually along a traveling direction is formed for guiding toward an air outlet 3 fresh air introduced through a fresh-air introducing port 5a of a fresh-air supply duct (supply air duct) 5 that will be mentioned later while swirling the fresh air effectively. In the supply air swirling space, airflow to be supplied to the air outlet 3 is previously formed into swirl flow having specified flow velocities.
Above the suction hood 10 in the supply air swirling space is provided a straightening plate 6 having a large number of airflow straightening holes 6a, 6a, . . . for straightening swirl flow formed as described above and for equalizing distribution of flow velocity of the swirl flow. The straightening plate 6 is formed of, for example, a punching plate, and outside and inside edges of the plate are fixed to the fresh-air supply chamber 4 and to a sleeve (coupling member) 20 surrounding a suction duct 2 that will be described later, by the medium of ring-like corner brackets 61 and 62, respectively.
The curved fresh-air introducing port 5a at an end of the fresh-air supply duct 5 is connected to and communicates with the fresh-air supply chamber 4 so as to introduce fresh air supplied from the outdoors in oblique tangential directions (swirling directions). The suction duct 2 is connected to and communicates with the suction hood 10, and the suction duct 2 is introduced downward through a top plate (apex) 4a of the fresh-air supply chamber 4 and extends (projects) cylindrically so that a suction port 2a at a lower end of the duct 2 is positioned in the vicinity of a surface of an air-collecting opening 10a of the suction hood 10. A fresh-air inlet end of the fresh-air supply duct 5 and an inside-air exhaust end of the suction duct 2 extend outdoors. At the ends extending outdoors (not shown) of the fresh-air supply duct 5 and the suction duct 2 are provided a fresh-air supply fan (air supply fan) and a suction fan (exhaust suction fan), respectively, that are composed of, for example, multiblade fans (sirocco fans). Those fans are driven so as to perform corresponding functions of supplying fresh air and sucking exhaust.
The sleeve 20 that can be penetrated by the suction duct 2 is fitted on the outer circumference of the suction duct 2 in the supply air swirling space. Besides the straightening plate 6, swirl flow generating stators 30a, 30a, . . . and the suction hood 10 are integrated with the fresh-air supply chamber 4 through the medium of the sleeve 20, as will be described later.
The suction duct 2 is inserted into the sleeve 20, the position of the suction port 2a is then set suitably as described above, and the duct is thereafter fixed.
On the circumference of the suction duct 2 and above the suction port 2a are provided auxiliary suction ports 2b, 2b, . . . for sucking inside air collected in the suction hood 10. At a lower end of the suction port 2a is provided an oil sump 7 having an oil sump groove 7a and having a cross section shaped like a letter U.
The air outlet 3 has a passage with a specified length, for example, between an inner circumferential surface of the fresh-air supply chamber 4 on the side of a lower end 4b and an outer circumferential surface of a shoulder 10c of the suction hood 10, has an all-around continuous annular opening, and is slantingly formed with a specified tilt angle so that center diameters of the outlet gradually expand toward the lower end of the outlet. In the air outlet passage are arranged a large number of swirl flow generating stators 30a, 30a, . . . that extend spirally downward with a specified tilt angle (radial angle) and that are spaced at specified intervals circumferentially.
The swirl flow generating stators 30a, 30a, . . . are formed as follows, in shape of gentle circular arcs each having specified length and width and extending parabolically with a specified radial angle. An outer circumferential edge of a flat circular metal plate 30 having a center aperture to be fitted on the sleeve 20 is slit parabolically and cut into strips in accordance with a number of the swirl flow generating stators 30a, 30a, . . . to be provided, and the cut strips are bent to a specified angle at specified positions (positions on radial lines) on the side of a main body 30b of the flat metal plate 30. The sleeve fitting aperture, that is, an inner circumference of the main body 30b of the flat metal plate is fitted and mounted from above on a lower end flange 20a of the sleeve 20 on the outer circumference of the suction duct 2, is positioned with use of round slots, and is fixed by screws, so that the swirl flow generating stators 30a, 30a, . . . are properly installed in the air outlet passage of the air outlet 3.
On underside of the lower end flange 20a of the sleeve 20 that supports the flat plate main body 30b of the swirl flow generating stators 30a, 30a, . . . in such a manner, a top plate section 10b of the dome-shaped suction hood 10 is integrally mounted by detachable mounting means such as slide engagement method so that attachment or detachment of the hood can easily be performed with an operation from below.
That is, attachment of the suction hood 10 is achieved, for example, as follows. On underside of the lower end flange 20a of the sleeve 20, hooked engaging pieces 13, 13, . . . each having a specified vertical gap are provided. On the side of the top plate 10b of the suction hood 10, on the other hand, rectangular engaging holes are provided. The engaging pieces 13, 13, . . . are arbitrarily fitted into the engaging holes, the hood is then slid and turned by a specified turning angle from the fitting position in a circumferential direction, and side edges of the holes thereby come into the gaps so as to achieve overlap engagement with completion of positioning of the hood. The hood is fixed by screws in the engagement position.
When the fresh-air supply fan on the side of the fresh-air supply duct 5 and the suction fan on the side of the suction duct 2 in the above configuration are driven, for example, fresh air guided into the fresh-air introducing port 5a through the fresh-air supply duct 5 is initially blown out into the supply air swirling space in tangential directions by a blast pressure from the fresh-air supply fan. The air is straightened by the straightening holes 6a, 6a, . . . of the straightening plate 6 while being swirled efficiently in the supply air swirling space, and resultant stable swirl flow with equalized flow velocities is supplied to the air outlet 3 provided between the inner circumferential surface of the fresh-air supply chamber 4 on the side of the lower end 4b and the outer circumferential surface of the shoulder 10c of the suction hood 10. When the swirl flow passes through the air outlet passage of the air outlet 3, the swirl flow generating stators 30a, 30a, . . . impart still larger vector in the swirling direction to the flow, which turns into stronger and stable spiral swirl airflow F1 with equalized air velocities in all circumferential directions and is blown out downward in oblique directions toward the outer circumference of the specified local region.
As a result, the blowoff swirl airflow F1 that is spiral and stable forms air curtain flow that reliably encircles air in the specified local region so as to prevent the air from diffusing into the surroundings. Inside the airflow F1 and along a central axis thereof, on the other hand, stable swirl suction airflow F2 is formed that vertically ascends like a tornado by the action of a suction force the suction fan exerts, in a direction opposite to the airflow F1, i.e., toward the suction port 2a extending tubularly up to the vicinity of the surface of the opening 10a of the suction hood 10 of the suction duct 2.
This arrangement makes possible reliable exhaust of air in the local region encircled by the air curtain flow composed of the spiral blowoff swirl airflow F1.
The air supply and exhaust apparatus with the above configuration, however, has some problems in such respects as the following.
In the configuration of the air supply and exhaust apparatus in FIG. 13, fresh air is introduced into the large supply air swirling space in the fresh-air supply chamber 4 through one supply duct 5, and it is therefore difficult to diffuse dynamic pressure of the introduced airflow and there is a limit to achieving uniform straightening effect all over the whole straightening surface of the straightening plate 6. That is, a portion of the airflow having a high dynamic pressure passes fast through the straightening plate 6, and a portion of the airflow having a low dynamic pressure passes slowly through the plate 6. Accordingly, swirl flow with equalized distribution of flow velocity cannot be generated, and blowoff airflow is therefore disturbed so that it is difficult to form reliable air curtain flow.
This problem becomes further remarkable in conventional air supply and exhaust apparatus that blow off air from the air outlet 3 without swirling the air by means of the swirl flow generating stators 30a, 30a, . . . and thereby form air curtain flow in contrast to the above apparatus.
The invention has been made in order to solve such a problem. An object of the invention is to provide an air supply and exhaust apparatus that is capable of diffusing effectively a dynamic pressure of air fed into a supply air space so as to equalize distribution of flow velocity of blowoff airflow from an air outlet and so as to be capable of forming more stable air curtain flow.
In order to attain the object, the invention is configured with the following means for problem solution.
The invention provide an air supply and exhaust apparatus for blowing out air that has a specified blast pressure and that is introduced into an upper region in a specified supply air space from a supply air duct, as air curtain flow, to an outer circumference of a specified local region through a lower air outlet that has a circumferential opening, while sucking air in the specified local region encircled by the air curtain flow, in a direction opposite to a direction in which the air is blown out, through a suction port located inside the air outlet into an upper region of a suction duct that is bored through a center part of the supply air space to extend outdoors, and exhausting the sucked air, characterized in that: the supply air space is divided by a partition plate into two upper and lower chambers, i.e., an upper first supply air space introducing air from the supply air duct and a second supply air space extending toward the air outlet; and the first and second supply air spaces are communicated with each other through annular straightening passages of small passage diameters extending vertically on an outer circumference of the suction duct.
In this manner, the supply air space into which air is supplied from the supply air duct is divided by the partition plate into two upper and lower chambers, i.e., the upper first supply air space into which air from the supply air duct is introduced and the lower second supply air space which extends toward the air outlet having the circumferential opening, and the first and second supply air spaces are communicated with each other through the annular straightening passages of the small passage diameters which extend vertically on the outer circumference of the suction duct extending through center parts of the supply air spaces. With this arrangement, air that flows into the first supply air space from the supply air duct with a dynamic pressure on a given level is temporarily interrupted by the partition plate and is uniformly dispersed in all over the first supply air space.
After that, the air flows evenly from all around directions into the annular straightening passages having stable shapes, the decreased passage diameters, and specified vertical lengths, and is throttled when flowing through the annular straightening passages in a specified period of time, so that flow velocities of the air are further equalized.
The airflow having the flow velocities further equalized is then forwarded radially outward evenly in the second supply air space that extends toward the air outlet as described above, and is blown out downward from the air outlet provided circumferentially, evenly in all around directions toward an outer circumference of the specified local region, so as to form air curtain flow that effectively encircles the local region.
With the configuration, as a result, air curtain flow having flow velocity distribution further equalized is formed without influence of deviated-flow pattern in the supply air space in which air is introduced, in contrast to the straightening plate described above.
In one embodiment of the air supply and exhaust apparatus, the straightening passage is defined by a cylinder wall provided a specified distance apart from the suction duct.
With the configuration, consequently, annular straightening passage having a double-cylinder structure is suitably shaped by the suction duct extending through the center parts of the first and second supply air spaces and by the cylinder wall surrounding the suction duct.
In one embodiment of the air supply and exhaust apparatus, the straightening passages are defined by a first cylinder wall provided a specified distance apart from the suction duct and having openings at both upper and lower ends thereof and by a second cylinder wall provided a specified distance apart from the first cylinder wall and having an opening only at a lower end thereof.
With the configuration, consequently, annular straightening passage having a nested-cylinder structure and having still greater straightening effect is suitably shaped by the suction duct extending through the center parts of the first and second supply air spaces, by the first cylinder wall provided around the suction duct, and by the second cylinder wall provided around the first cylinder wall. In this configuration, air supplied into the first supply air space from the supply air duct is initially interrupted by the partition plate, is uniformly dispersed in all over the first supply air space, thereafter flows upward, and thereafter flows downward while being throttled.
In one embodiment of the air supply and exhaust apparatus, straightening plates having a large number of straightening holes are provided in the straightening passage.
Where the straightening plates having the large number of straightening holes are provided in the straightening passage that achieves an efficacious straightening effect based on such a throttling effect as described above, flow velocities of supply air that includes deviated flow when flowing into the straightening passage are further effectively straightened when the air passes through the large number of straightening holes, and distribution of the flow velocities are thereby equalized further.
In one embodiment of the air supply and exhaust apparatus, swirl flow generating stators for swirling spirally air that is blown out are provided in the air outlet.
When supply air having flow velocity distribution equalized by the effect of the straightening passages as described above passes through the air outlet 3 with the configuration, the swirl flow generating stators impart vector in swirling direction to the supply air, which turns into stable spiral swirl airflow F1 having air velocities equalized in all circumferential directions and is blown out downward to the outer circumference of the specified local region.
As a result, the blowoff swirl airflow F1 that is spiral and stable forms further reliable air curtain flow that encircles air in the specified local region so as to prevent diffusion thereof into surroundings.
In one embodiment of the air supply and exhaust apparatus, the supply air duct supplies air in swirling directions into the first supply air space.
With the configuration, air flows into the first supply air space in tangential directions from the supply air duct, and therefore air to be supplied to the air outlet through the straightening passages is previously formed into swirl flow, so that air curtain flow which is ultimately formed is further stabilized. Where the swirl flow generating stators are provided in the air outlet, in particular, the configuration further improves a function of generating swirl flow that is achieved by the swirl flow generating stators.
As a result, satisfactory air curtain flow that is closed more tightly is formed.
In accordance with the air supply and exhaust apparatus of the invention, as described above, flow velocity distribution of the blowoff airflow can be equalized and therefore exhaust from the specified local region can be achieved efficiently.
In the case that the air supply and exhaust apparatus is applied, for example, to a local ventilator, accordingly, ventilation of the specified local region can be achieved efficiently enough with reliable air curtain flow having stable flow velocity distribution.